1. Field of the Invention
The present invention relates to a process and an apparatus for forming a color image with a powder toner and a liquid ink.
2. Related Background Art
As typical methods for forming a color image by a printer, copying machine, facsimile (FAX) or the like, there have heretofore been used an electrophotographic system and an ink-jet system.
In the electrophotographic system, for example, a toner image is formed on a photosensitive drum by charging, exposing and developing means provided around the photosensitive drum, and the toner image is transferred to a recording medium and then fixed by a fixing means. In this case, an apparatus may be constructed in a relatively small size in the case of a monochrome image. However, in the case of a color image, an enlarged apparatus and an increase in cost become a problem.
On the other hand, the latter ink-jet system is such a system that an ink is directly ejected on a recording medium from a recording head to form an ink image. According to this system, a color image can be formed by a relatively small-sized apparatus compared with the electrophotographic system. However, this system is required to be improved in that the printing speed is slow compared with the electrophotographic system, and bleeding between colors occurs when a recording medium is general-purpose plain paper to incur a possibility that the quality of an image formed may be deteriorated.
In order to solve these problems to be improved, for example, Japanese Patent Application Laid-Open Nos. 7-205542, 7-223362, 9-94942 and 11-277814 have proposed image forming processes using both image forming means according to the electrophotographic system and image forming means according to the ink-jet system.
However, the process described in Japanese Patent Application Laid-Open Nos. 7-205542 and 7-223362 is such that recording is conducted by the electrophotographic system using a powder toner, and ink-jet recording is then conducted with a water-based ink, and incurs a possibility that the water-based ink may be repelled by the toner between a toner image-formed portion and an ink image adjacent thereto or at an overlapped portion therebetween according to the composition of the toner previously attached on recording paper or by silicone oil or the like used in a fixing device. In addition, in the case of formation of a color image, an image formed may undergo bleeding due to color mixing between water-based color inks in some cases. Further, a recording medium such as paper swells right after the water-based ink is applied to the recording medium to cause waviness, which may become a cause of wrinkles and/or curling. Japanese Patent Application Laid-Open No. 11-277814 describes an image forming apparatus having a means for changing over a system for forming a black image between the electrophotographic system and the ink-jet system based on the attribute of an object image in order to solve an image failure at an overlapped portion between a toner image and an ink image. However, such an image forming apparatus requires to judge the attribute of the object image, and so a complicated device is necessary. On the other hand, Japanese Patent Application Laid-Open No. 9-94942 states that hot-melt inks such as pigment inks can be used for an ink-jet output mechanism in addition to inks comprising a water-soluble dye. In the case where the hot-melt ink is used, however, heat is applied to the ink-jet output mechanism, so that a toner attached to recording paper may be melted out in some cases to cause an image failure at an overlapped portion between a toner image and an ink-applied area. Further, when the hot-melt ink is applied so as to overlap with a toner image, the hot-melt ink may be swollen at the overlapped portion.
The present invention has been made with the foregoing problems in view and has as its object the provision of image forming process and apparatus, by which a good-quality image can be formed while avoiding enlarging the apparatus and increasing the cost thereof, and neither wrinkle nor curling occurs.
The present inventors have investigated various liquid inks and processes with a view toward achieving the above object. As a result, it has been found that when non-aqueous liquid inks are used, the inks are hard to be repelled by a toner between a toner image-formed portion and an ink image adjacent thereto or at an overlapped portion therebetween, and wrinkles and curling are hard to occur because bleeding due to color mixing between the inks becomes hard to occur on an image formed, and a recording medium is not swollen, thus leading to completion of the present invention.
According to the present invention, there is provided an image forming process for forming an image on a recording medium, which comprises the steps of applying a melting powder toner to the recording medium to fix the toner by heating and applying liquid inks to the recording medium, wherein the liquid inks contain a colorant in a non-aqueous solvent.
In the image forming process, the melting powder toner may preferably contain a black colorant.
At least three liquid inks of a yellow, magenta and cyan colors may be preferably used as the liquid inks.
At least four liquid inks of a yellow, magenta, cyan and black colors may also be preferably used as the liquid inks.
In the step of applying the liquid inks, the inks may preferably be applied to the recording medium by an ink-jet recording method.
According to the present invention, there is also provided an image forming apparatus comprising a means for forming an image with a melting powder toner and a means for forming an image with liquid inks, wherein the liquid inks contain a colorant in a non-aqueous solvent.